In some corners of the world, one wrong sip can put a serious cramp in your travel plans. Try these common-sense steps to prevent—and bounce back from—the ultimate vacation bummer.

I'm planning a trip to Peru. Is it inevitable that I'll get diarrhea?

What's that I hear? A collective "Ewww, gross"? Let's settle down and demystify this common travel ailment, officially called travelers' diarrhea (TD) but also known by a variety of colorful nick-names, including turista, Montezuma's revenge, Delhi belly, and the Turkey trot, depending on where you are in the world.

Whatever you call it, the symptoms are, alas, universally awful: urgent sprints to the bathroom, abdominal cramps, sometimes nausea and vomiting, and in serious cases dehydration and fever. The Centers for Disease Control and Prevention (CDC) estimates that TD hits up to 50 percent of international travelers and up to 70 percent of those visiting high-risk regions, including most of Asia, the Middle East, Africa, and Central and South America.

But TD is not inevitable. The main cause is food and water contaminated with bacteria (such as E. coli and salmonella), viruses, and parasites from animal feces. When those pesky microorganisms hit your gastrointestinal tract, your gut essentially erupts in an effort to get rid of the invaders. Your odds of getting sick are higher when a rudimentary water system—such as those in developing regions—fails to adequately separate tap water from waste water. What's more, food-safety standards from farm to table are usually less stringent than in the U.S., Western Europe, Australia, New Zealand, and Japan. Meat can become contaminated at the slaughterhouse, fruits and vegetables come in contact with manure-based fertilizers, and restaurant workers often aren't taught to wash their hands before handling food-even after using the toilet.

What can I do to stay safe?

One easy rule of thumb: If your lodgings don't allow you to flush toilet paper, don't drink the water. It's a sign you're visiting a region with an unsafe water supply. That also means no ice cubes or diluted juices or cocktails with water or ice, no swallowing shower water, and no brushing your teeth with tap water (a BT reader recently recommended placing an airline luggage tag over your hotel bathroom's faucet as a reminder). Instead, drink bottled sodas and carbonated waters (unfortunately, some bottled still water may be contaminated in some countries). Or purify your own water: One option is to bring an electric kettle and boil tap water for at least one minute. Stuart Rose, M.D., founder of the Travel Medicine Center of Western Massachusetts, suggests that you bring iodine tablets, which kill bacteria in about 10 minutes.

As for food, "Boil it, peel it, or forget it" has been the standard recommendation. It means you should eat only foods that are thoroughly cooked (that goes for vegetables as well as meats, since raw veggies were likely washed in tap water) or that you yourself have to peel (like oranges and bananas), which ensure that only your well-washed hands have come in contact with the fruit. In high-risk regions, packaged foods—especially those that you bring with you from home—are going to be your safest eating option. (See below for our list of "Credible Edibles.")

Oh, and I should also mention: Your mom was right when she insisted you wash your hands before dinner. Pack a bar of soap and hand-sanitizing wipes or alcohol-based gel such as Purell. You may have no say in whether a restaurant worker washes his hands before handling your food, but keeping your own paws pure will go a long way toward keeping invaders out of your GI tract. Cleaning hands with soap and warm tap water (even in high-risk regions) is safe, says Cedric Spak, M.D., M.P.H., an infectious disease specialist at Baylor University Medical Center at Dallas, as long as you wash your hands vigorously and thoroughly dry them.

Are street food carts off-limits?

No, but (of course) there's a caveat. Food prepared at a street cart is not inherently more or less safe than food at the upscale bistro around the corner, says Spak. What matters—and this goes for any restaurant, cart, or home-cooked meal—is how scrupulously hands, surfaces, and food are kept clean and how efficiently the food is served. Here are the things you want to watch for when deciding whether or not to eat from a street cart:

Pick a cart with a long line and quick turnover, which means food is hot and fresh. Certain vendors are popular because their food is tastier and safer-it's worth the extra minutes in line.

Bring your own bowl and utensils. It may sound impractical, but in developing regions, improper washing of serving dishes may transmit microorganisms that can make you sick.

Make sure food is served piping hot. If it's been left out to cool, it could be harboring a growing colony of bacteria.

Fly from flies. Never eat food that isn't protected from insects, which can contaminate even freshly cooked dishes.

Go with your instincts. If surfaces don't look clean and you don't see a place where workers can wash their hands, pass.

Return to a cart you've enjoyed. Finding a vendor serving safe, delicious food can be the beginning of a beautiful friendship-he may even share recipes if you ask.

Are there medications I can take while traveling that will make me immune to TD?

Some people swear that taking Pepto-Bismol may reduce TD risk, and Rose says that the active ingredient, bismuth, has some antibacterial properties. However, the product is meant to treat stomach upset, not prevent it, and you should check with your doctor before loading up your suitcase with "pink magic."

Credible Edibles

These highly portable foods can help ensure that you have the protein, carbs, and vitamins you need even in the sketchiest locales.

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